0:
sub {
    while (1) {
        print $_;
    }
}

1:
sub {
    while (1) {
        print $_;
    }
}

2:
sub {
    while (()) {
        print $_;
    }
}

3:
sub {
    print $_ while ();
}

4:
sub {
    print $_ while ();
}

5:
sub {
    print $_ until ();
}

6:
sub {
    print $_ until ();
}